The present invention relates to a lubrication system for a vehicle driveline master clutch which utilizes a ball ramp mechanism to load a clutch pack and more specifically to a lubrication system for a vehicle driveline master clutch which utilizes a ball ramp actuator to load a clutch pack where the master clutch includes a lubrication pump to direct fluid flow from a transmission lubricant sump and direct it to the master clutch and through the gear change transmission.
Driveline master clutches commonly use a plurality of springs to clamp a friction disc to an engine flywheel. The clamping springs are normally disposed within a pressure plate assembly which is bolted to the flywheel. The friction discs are splined to rotate with a transmission input shaft which, when rotated, provides motive power to the driveline and wheels of the vehicle. A mechanical linkage operated by a driver is used to control the engagement and disengagement of the master clutch. The clutch is typically a dry clutch when no lubricant is required. The master clutch is typically located between a prime mover such as an internal combustion engine and a gear change transmission.
Efforts to automate the operation of the master clutch to eliminate the need for driver operation are currently underway. Thus, it is known to make use of a hydraulic actuator or an electric motor actuator to operate the master clutch release mechanism in response to a control signal generated by a control microprocessor in response to a multiplicity of sensor outputs which are used to determine the vehicle operating conditions and hence the desired operation of the master clutch. Furthermore, the use of a ball ramp actuator to operate a driveline master clutch is known in the art. U.S. Pat. Nos. 5,441,137; 5,469,948; 5,505,285; 5,651,437; 5,810,141; 5,910,061; 5,964,330; and RE 36,502 assigned to the same assignee as this application, all of which are hereby expressly incorporated by reference, disclose methods of using a ball ramp actuator to supply the clamping force on a clutch disc and could, in the alternative, be used to supply a release force against a clutch apply spring.
Typically, a ball ramp actuator is activated when an electrical current is supplied to a coil thereby producing an electromagnetic field in a coil pole which applies a retarding force to an armature which rotates with an input shaft. The rotating armature is nonrotatably connected to an annular control ring which has a plurality of control ramps or grooves formed in the face of the control ring which vary in axial depth. An annular activation ring which rotates with an output shaft has a like number of variable depth activation grooves formed therein which oppose those formed in the control ring where a corresponding number of rolling elements are trapped between the control and activation grooves. As a retarding force is applied to the control plate by the armature, the rotational movement of the control plate relative to the activation plate causes the rolling elements to simultaneously traverse the control grooves and the activation grooves thereby causing an increase in separation distance between the control and activation plates which is used to provide a clamping force on a device such as a clutch friction disc.
The prior art ball ramp actuators used in the operation of the master clutch or other driveline coupling system such as a differential or transfer case could be improved by improving the flow of lubricating/cooling fluid through the clutch. It would also be an advantage if the clutch lubrication system could make use of the same lubricant as that used in the transmission. It would also be an advantage if the lubrication system for the clutch could be used with either a dry or wet sump transmission lubrication system.
The present invention results in an improvement in the lubrication system of a ball ramp clutch which can be used in a variety of vehicle driveline applications to provide a clamping load on a frictional clutch pack. The present invention provides for the common use of the lubricant used in a gear change transmission for use in the ball ramp clutch irrespective of whether it is a dry sump or a wet sump system. This unique solution reduces package size, simplifies the lubrication system, reduces cost and improves performance.
The present invention improves the performance and durability of a ball ramp actuated master clutch assembly by eliminating the need for separate lubrication systems for the ball ramp clutch and the gear change transmission. The present invention also improves the performance and durability of a ball ramp actuated master clutch assembly by eliminating one-way clutches with the use of indexing plates to limit the relative rotational travel of the control ring and the actuation ring of the ball ramp actuator which is used to apply an axial clamping load on a clutch pack. One indexing plate limits the rotation of the control ring of the ball ramp mechanism, and a second indexing plate limits the rotation of the activation ring, thereby allowing unidirectional grooves to be used in the control ring and the activation ring. Using the indexing plates of the present invention, the ball ramp mechanism, when energized, can only further compress the clutch pack with clutch slippage thereby preventing any break in clutch engagement when the torque flow in the driveline reverses direction from a drive mode into a driven mode. The torque flow in the driveline is in a drive mode when the engine is supplying power to the input shaft of the clutch assembly and in a driven mode when the engine is absorbing power from the input shaft of the clutch assembly. The indexing plates do not always prevent rotation in an undesired direction as with the one-way clutches disclosed in U.S. Ser. No. 09/940,821 but may permit limited rotation in an undesired manner until the index plates hit against a respective stop formed on the control plate and the activation plate.
The present invention also results in an improvement in the operational characteristics of a ball ramp actuator which can be used in a variety of vehicle driveline applications to supply a clamping load to a frictional clutch pack. The present invention provides a unidirectional apply ball ramp function which applies the clutch irregardless of torque flow along with significantly increased frictional damping in the ball ramp mechanism itself to control and stabilize the ball ramp mechanism thereby improving the operation of the master clutch or other driveline device.
To improve the operation of the ball ramp mechanism, the stability is improved by significantly increasing the frictional damping using an intermediate plate disposed between the activation plate and the control plate where the intermediate plate rotates with the output shaft and hub and the activation plate rotates with the activation ring and the control plate rotates with the control ring. Either the activation plate or the control plate must slip relative to the intermediate plate (which rotates with the output shaft) for the ball ramp mechanism to increase the clamp load on the clutch pack. Note that the torque flow from the input shaft to the output shaft can be reversed so that the torque flows from the output shaft to the input shaft and the ball ramp clutch assembly will continue to provide the desired functionality.
One provision of the present invention is to provide a vehicle master clutch using a ball ramp actuator to load a clutch pack where the master clutch uses a common lubrication system with a gear change transmission.
Another provision of the present invention is to provide a vehicle master clutch using a ball ramp actuator to load a clutch pack where the master clutch includes an integral pump to pressure a lubricant flow within a ball ramp mechanism and clutch pack.
Another provision of the present invention is to provide a master clutch having a ball ramp mechanism to load a clutch pack where the lubrication system is pressurized using a gerotor pump mounted within the ball ramp master clutch which draws lubricant from a lubricant sump and supplies lubricant to both the clutch and a change gear transmission.
Still another provision of the present invention is to provide a ball ramp actuator to actuate a driveline master clutch which is joined to a gear change transmission, both the master clutch and the transmission having an improved lubrication system.